HADOOP-4141. Fix bug in ScriptBasedMapping causing potential infinite loop on misconfigured hadoop-site. Contributed by Aaron Kimball.

git-svn-id: https://svn.apache.org/repos/asf/hadoop/core/trunk@714107 13f79535-47bb-0310-9956-ffa450edef68

CHANGES.txt

@@ -158,6 +158,9 @@ Trunk (unreleased changes)
     HADOOP-4606. Fix cygpath error if the log directory does not exist.
     (szetszwo via omalley)
 
+    HADOOP-4141. Fix bug in ScriptBasedMapping causing potential infinite
+    loop on misconfigured hadoop-site. (Aaron Kimball via tomwhite)
+
 Release 0.19.0 - 2008-11-18
 
   INCOMPATIBLE CHANGES

src/core/org/apache/hadoop/net/ScriptBasedMapping.java

@@ -38,6 +38,14 @@ implements Configurable
     super(new RawScriptBasedMapping());
   }
   
+  // script must accept at least this many args
+  static final int MIN_ALLOWABLE_ARGS = 1;
+  
+  static final int DEFAULT_ARG_COUNT = 100;
+  
+  static final String SCRIPT_FILENAME_KEY = "topology.script.file.name";
+  static final String SCRIPT_ARG_COUNT_KEY = "topology.script.number.args";
+  
   public ScriptBasedMapping(Configuration conf) {
     this();
     setConf(conf);
@@ -59,8 +67,8 @@ implements Configurable
   private static Log LOG = 
     LogFactory.getLog(ScriptBasedMapping.class);
   public void setConf (Configuration conf) {
-    this.scriptName = conf.get("topology.script.file.name");
-    this.maxArgs = conf.getInt("topology.script.number.args", 100);
+    this.scriptName = conf.get(SCRIPT_FILENAME_KEY);
+    this.maxArgs = conf.getInt(SCRIPT_ARG_COUNT_KEY, DEFAULT_ARG_COUNT);
     this.conf = conf;
   }
   public Configuration getConf () {
@@ -90,7 +98,20 @@ implements Configurable
         String switchInfo = allSwitchInfo.nextToken();
         m.add(switchInfo);
       }
+      
+      if (m.size() != names.size()) {
+        // invalid number of entries returned by the script
+        LOG.warn("Script " + scriptName + " returned "
+            + Integer.toString(m.size()) + " values when "
+            + Integer.toString(names.size()) + " were expected.");
+        return null;
+      }
+    } else {
+      // an error occurred. return null to signify this.
+      // (exn was already logged in runResolveCommand)
+      return null;
     }
+    
     return m;
   }
   
@@ -101,6 +122,13 @@ implements Configurable
     }
     StringBuffer allOutput = new StringBuffer();
     int numProcessed = 0;
+    if (maxArgs < MIN_ALLOWABLE_ARGS) {
+      LOG.warn("Invalid value " + Integer.toString(maxArgs)
+          + " for " + SCRIPT_ARG_COUNT_KEY + "; must be >= "
+          + Integer.toString(MIN_ALLOWABLE_ARGS));
+      return null;
+    }
+    
     while (numProcessed != args.size()) {
       int start = maxArgs * loopCount;
       List <String> cmdList = new ArrayList<String>();

src/test/org/apache/hadoop/net/TestScriptBasedMapping.java

@@ -0,0 +1,46 @@
+/**
+ * Licensed to the Apache Software Foundation (ASF) under one
+ * or more contributor license agreements.  See the NOTICE file
+ * distributed with this work for additional information
+ * regarding copyright ownership.  The ASF licenses this file
+ * to you under the Apache License, Version 2.0 (the
+ * "License"); you may not use this file except in compliance
+ * with the License.  You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ */
+package org.apache.hadoop.net;
+
+import java.util.ArrayList;
+import java.util.List;
+
+import org.apache.hadoop.conf.Configuration;
+
+import junit.framework.TestCase;
+
+public class TestScriptBasedMapping extends TestCase {
+
+  public void testNoArgsMeansNoResult() {
+    ScriptBasedMapping mapping = new ScriptBasedMapping();
+
+    Configuration conf = new Configuration();
+    conf.setInt(ScriptBasedMapping.SCRIPT_ARG_COUNT_KEY,
+        ScriptBasedMapping.MIN_ALLOWABLE_ARGS - 1);
+    conf.set(ScriptBasedMapping.SCRIPT_FILENAME_KEY, "any-filename");
+
+    mapping.setConf(conf);
+
+    List<String> names = new ArrayList<String>();
+    names.add("some.machine.name");
+    names.add("other.machine.name");
+
+    List<String> result = mapping.resolve(names);
+    assertNull(result);
+  }
+}